• Volume 84, Issue 1

January 2015,   pages  1-165

• General editorial on publication ethics

• New exact wave solutions for Hirota equation

In this paper, we construct the topological or dark solitons of Hirota equation by using the first integral method. This approach provides first integrals in polynomial form with a high accuracy for two-dimensional plane autonomous systems. Exact soliton solution is constructed through the established first integrals. This method is a powerful tool for searching exact travelling solutions of nonlinear partial differential equations (NPDEs) in mathematical physics.

• Analytical solution of population balance equation involving aggregation and breakage in terms of auxiliary equation method

This paper presents an effective analytical simulation to solve population balance equation (PBE), involving particulate aggregation and breakage, by making use of appropriate solution(s) of associated complementary equation via auxiliary equation method (AEM). Travelling wave solutions of the complementary equation of a nonlinear PBE with appropriately chosen parameters is taken to be analogous to the description of the dynamic behaviour of the particulate processes. For an initial proof-of-concept, a general case when the number of particles varies with respect to time is chosen. Three cases, i.e. (1) balanced aggregation and breakage, (2) when aggregation can dominate and (3) breakage can dominate, are selected and solved for their corresponding analytical solutions. The results are then compared with the available analytical solution, based on Laplace transform obtained from literature. In this communication, it is shown that the solution approach proposed via AEM is flexible and therefore more efficient than the analytical approach used in the literature.

• Stability analysis of fractional-order generalized chaotic susceptible–infected–recovered epidemic model and its synchronization using active control method

This paper presents the synchronization between a pair of identical susceptible–infected–recovered (SIR) epidemic chaotic systems and fractional-order time derivative using active control method. The fractional derivative is described in Caputo sense. Numerical simulation results show that the method is effective and reliable for synchronizing the fractional-order chaotic systems while it allows the system to remain in chaotic state. The striking features of this paper are: the successful presentation of the stability of the equilibrium state and the revelation that time for synchronization varies with the variation in fractional-order derivatives close to the standard one for different specified values of the parameters of the system.

• Increased-order generalized synchronization of chaotic and hyperchaotic systems

This paper presents increased-order generalized synchronization (GS) of chaotic and hyperchaotic systems with different order based on active control technique. By this technique, we design suitable control functions to achieve GS between (i) a new three-dimensional (3D) chaotic system and four-dimensional (4D) hyperchaotic Lorenz system and (ii) four-dimensional hyperchaotic Lorenz system and five-dimensional (5D) hyperchaotic Lorenz system. The corresponding numerical simulation results are presented to verify the effectiveness of this technique.

• Robust antisynchronization of chaos using sliding mode control strategy

The paper proposes a sliding mode control strategy-based scheme for achieving anti-synchronization between two coupled non-linear chaotic systems. The method works irrespective of whether the systems under consideration possess or lack inverse symmetry. Using a linear sliding surface, a sliding mode control input and a non-linear coupling function are designed that synchronizes the systems antiphase. Finite-time convergence of the method is established. The controller is also robust to all forms of bounded perturbations and this robustness can be easily achieved by tuning of a single controller parameter and introduction of a control vector. The controller is also made chattering-free by producing a continuous analogue of the discontinuous control input. The effectiveness of the method is established by implementing it to antisynchronize chaotic Sprott systems and Rossler systems. The results are also verified through numerical simulation work.

• Form factors and charge radii in a quantum chromodynamics-inspired potential model using variationally improved perturbation theory

We use variationally improved perturbation theory (VIPT) for calculating the elastic form factors and charge radii of $D$, $D_{s}$, $B$, $B_{s}$ and $B_{c}$ mesons in a quantum chromodynamics (QCD)-inspired potential model. For that, we use linear-cum-Coulombic potential and opt the Coulombic part first as parent and then the linear part as parent. The results show that charge radii and form factors are quite small for the Coulombic parent compared to the linear parent. Also, the analysis leads to a lower as well as upper bounds on the four-momentum transfer $Q^{2}$, hinting at a workable range of $Q^{2}$ within this approach, which may be useful in future experimental analyses. Comparison of both the options shows that the linear parent is the better option.

• Systematic of signature inversion in $(h_{11/2})_{\text{p}}\otimes (i_{13/2})_{\text{n}}$ for odd–odd nuclei in rare-earth nuclei

Systematic features of the signature inversion phenomenon in $(h_{11/2})_{\text{p}}\otimes (i_{13/2})_{\text{n}}$ in doubly-odd rare-earth nuclei are presented. These features are generally observed in high-$j$ orbitals, mainly, in $(h_{9/2})$, $(h_{11/2})$ and $(i_{13/2})$. Calculations are carried out within the framework of the two quasiparticle plus rotor model (TQPRM) to explain strong odd–even staggering and signature inversion observed in these high-$j$ orbitals. The shifting of point of inversion to lower/higher spin with the increase in neutron/proton numbers is well explained by the calculations. It is found that 1/2[541] proton orbital of $h_{9/2}$ is necessary in the lower mass region to obtain the point of inversion.

• On the momentum distribution of particles participating in nuclear stopping

Nuclear stopping is studied as a function of incident energy and charge of the fragment produced in central heavy-ion collisions (HIC) of $^{197}_{79}$Au+$^{197}_{79}$Au and $^{58}_{28}$Ni+$^{58}_{28}$Ni using stopping parameter VARXZ. Various momentum constraints were imposed to get better insight into the stopping. The comparison of measured and calculated values of stopping for protons reveals the significance of these constraints. Maximum stopping is obtained for the particles lying in the lowest range of the momentum distribution at all incident energies.

• Alpha decay properties of heavy and superheavy elements

Analysing accurately the lifetimes of 𝛼-decay chains is an important tool to detect and study the properties of superheavy nuclei. 48Ca is used in the synthesis of superheavy nuclei $Z$ = 106−118 at Dubna. The experimental work of 48Ca projectiles at Dubna has given an opportunity to study the superheavy element (SHE). Here, the 𝛼-decay properties for $Z$ = 106–118 are evaluated using our CYE model and are compared with the available experimental and theoretical values.

• Half-width at half-maximum, full-width at half-maximum analysis for resolution of asymmetrically apodized optical systems with slit apertures

Resolution for the modified point spread function (PSF) of asymmetrically apodized optical systems has been analysed by a new parameter half-width at half-maximum (HWHM) in addition to the well-defined parameter full-width at half-maximum (FWHM). The distribution of half-maximum energy in the centroid of modified PSF has been investigated in terms of HWHM on good side and HWHM on bad side. We observed that as the asymmetry in PSF increases, FWHM of the main peak increases and then decreases and is being aided by the degree of amplitude apodization in the central region of slit functions. In the present study, HWHM (half-width at half-maximum) of the resultant PSF has been defined to characterize the resolution of the detection system. It is essentially a line of projection, which measures the width of the main lobe at its half-maximum position from the diffraction centre and has been computed for various amplitudes and antiphase apodizations of the slit aperture. We have noticed that HWHM on the good side decreases at the cost of the increased HWHM on the bad side in the presence of asymmetric apodization.

• The influence of atomic coherence and dipole–dipole interaction on entanglement of two qubits with nondegenerate two-photon transitions

Considering two artificial identical atoms interacting with two-mode thermal field through non-degenerate two-photon transitions, this paper studies the influence of atomic coherence and dipole–dipole interaction on the entanglement of two qubits. It is found that the entanglement is greatly enhanced by these mechanisms.

• Dust-ion-acoustic Gardner double layers in a dusty plasma with two-temperature electrons

The properties of dust-ion-acoustic Gardner double layers (DIA GDLs) in an unmagnetized dusty plasma, whose constituents are negatively-charged stationary dust, inertial ions, and Boltzmann electrons of two distinct temperatures, are rigorously investigated by employing the reductive perturbation method: Gardner approach. The standard Gardner equation is derived, and its double layer (DL) solution is obtained. It has been shown that the properties of the DIA GDLs are significantly modified by some plasma parameters (viz. 𝜎 = 𝑇e1/𝑇e2, 𝜇e1 = 𝑛e10/𝑛i0, and 𝜇e2 = 𝑛e20/𝑛i0, where 𝑇e1 (𝑇e2) is the cold (hot) electron temperature, 𝑛e10 (𝑛e20) is the cold (hot) electron number density at equilibrium, and 𝑛i0 is the ion number density at equilibrium). The implications of our investigation in understanding the basic features of nonlinear electrostatic perturbations observed in many space plasma systems and laboratory devices are briefly discussed.

• Planar dust-acoustic waves in electron–positron–ion–dust plasmas with dust-size distribution under higher-order transverse perturbations

Propagation of small but finite nonlinear dust-acoustic solitary waves are investigated in a planar unmagnetized dusty plasma, which consists of electrons, positrons, ions and negatively charged dust particles with different sizes and masses. A Kadomtsev–Petviashvili (KP) equation is obtained by using reductive perturbation method. The effect of positron density and positron–electron temperature ratio on dust-acoustic solitary structures are studied. Numerical results show that the increase in positron number density increases the amplitude of hump-like solitons but decreases the dip-like solitary waves. Furthermore, increase in the positron–electron temperature ratio results in the decrease of the amplitude of dip-like solitary waves. It seems that both the dipand hump-like solitary waves can exist in this system. Our results also suggest that the dust-size distribution has a significant role on the amplitude of the solitary waves.

• Effect of doping of N and B atoms on thermoelectric properties of C60 molecule

In this work, the doping effect on the thermoelectric properties of the C60 molecule (fullerene) was studied by considering inelastic electron–phonon interactions. It is seen that the maximum value of thermal conductance (𝑘max) with respect to the molecules are 𝑘max(C59N) &lt; 𝑘max(C60) &lt; 𝑘max(C59B). Also, the oscillatory behaviour of thermal conductance is dramatically dependent on the type of molecules. The values of figure of merit (ZT) against energy and with respect to the type of molecules are between 0.25 × 10−5 and 0.194 × 10−3 and effect of the type of molecules is small on the minimum value of ZT.

• # Pramana – Journal of Physics

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• # Editorial Note on Continuous Article Publication

Posted on July 25, 2019